A motor control device for a brushless motor includes an electric current detecting section, a rotating position detecting section, a dq-axis target electric current value computing section, a dq-axis electric current computing section, a d-axis voltage command value computing section, and a q-axis voltage command value computing section. The electric current detecting section detects an electric current flowing in an armature coil of a motor. The rotating position detecting section detects a rotor rotating position of the motor. The dq-axis target electric current value computing section computes a d-axis target electric current value and a q-axis target electric current value. The dq-axis electric current computing section obtains a d-axis electric current and a q-axis electric current based on an armature coil electric current and a rotor rotating position. The d-axis voltage command value computing section obtains a d-axis voltage command value based on PI computation on a d-axis deviation between the d-axis target electric current value and the d-axis electric current so as to reduce the d-axis deviation. The q-axis voltage command value computing section obtains a q-axis voltage command value based on PI computation of a q-axis deviation between the q-axis target electric current value and the q-axis electric current so as to reduce the q-axis deviation. Based on the d-axis voltage command value and the q-axis voltage command value thus obtained and the detected rotor rotating position, the motor control device applies a voltage to the armature coil. Accordingly, a rotor torque is generated.
On the other hand, non-interference control in which a non-interference control amount is added to a PI computation value is known (refer to US 2001/0005121A1). Non-interference control is control for determining a voltage command value so as to compensate a speed electromotive force generated inside the motor due to the rotation of the rotor. It is expected that the non-interference control will effectively reduce deterioration in responsiveness and following capability caused by a speed electromotive force.